Spinal surgeries are commonly used in the medical profession to treat spinal conditions that result when functional segmental units of the spine are moved out of proper position or otherwise damaged. Examples of procedures used to treat spinal conditions include disc replacement, laminectomy, and spinal fusion.
Following certain spinal procedures, such as spinal fusion, it is typically desirable to stabilize the spine by preventing movement between the vertebrae while the spine heals. This act of stabilizing the spine by holding bones in place during healing has greatly improved the success rate of spinal fusions and other procedures.
With spinal stabilization procedures, a combination of metal screws and rods creates a solid “brace” that holds the vertebrae in place. These devices are intended to stop movement from occurring between the vertebrae. These metal devices give more stability to the fusion site and allow the patient to be out of bed much sooner.
During the spinal stabilization procedure, pedicle screws are placed through the pedicle bone on the back of the spinal column. Each screw inserts through the pedicle and into the vertebral body, one on each side. The screws grab into the bone of the vertebral body, giving them a good solid hold on the vertebra. Once the screws are placed on the vertebra, they are attached to metal rods that connect all the screws together. When everything is bolted together and tightened, this creates a stiff metal frame that holds the vertebrae still so that healing can occur.
Posterior dynamic stabilization (PDS) generally refers to such a stabilization procedure where dynamic rods are positioned between the pedicle screws. These dynamic rods can generally bend, extend, compress, or otherwise deform in order to allow some limited movement between the pedicle screws. By allowing this limited movement between the pedicle screws and the associated segmental unit, less strain is placed on adjoining, non-stabilized functional segmental units during patient movements.
Depending upon the procedure performed, a multi-level stabilization system is often desired. These multi-level systems extend over a plurality of segmental units. Multi-level stabilization systems may also be PDS systems, incorporating dynamic flexible rods into the system. With such multi-level PDS systems, it is often important to properly center the dynamic portion of a rod between adjacent pedicle screws in order to properly provide limited movement between adjacent vertebrae. However, because of the difference in each unique patient size, and the difference in segmental unit sizes within a given patient, it is difficult to construct a multi-level PDS system where the dynamic portion of each rod is properly centered between adjacent pedicle screws.
Accordingly, it would be advantageous to provide an easy to use, modular PDS system that allows a surgeon to create a multi-level stabilization system including various dynamic segments. It would be of further advantage if such system could include various dynamic rods connected in series while requiring a minimal number of components capable of accommodating a large range of different patient sizes and anatomies. It would also be advantageous if the dynamic portions of the rods in such a multi-level stabilization system could be easily centered between pedicle screws.